Choices in 1,000 Watt and Higher Power Amps

What are your experiences out there with high powered power amps, 1000 watts and higher?

I am looking for comments on both power amps and various preamps.

I run an SWR Bass 750 to power my custom built cabinets that run inefficient bass drivers that are dead flat to 28 Hz. This is a fundamental design tradeoff between high SPL (loudness) vs low frequency extension.

I wanted low frequency response, and choose to make up for it with a higher powered amp. My SWR 750 runs at full Gain, and about 3/4 maximum Master Volume, so it is fast approaching the out-of-gas point.

Yes, I already know that 10x the amplifier power is required to sound twice as loud.

Let me be a smart guy and suggest coupling your nice speakers to a big horn cabinet! Horn loading is one way to get around the SPL vs. Low F conundrum, but the cost is then size and weight!

As I alluded in the other thread, I've upgraded my power. Part of the process involved looking at separate power amps vs. buying another complete bass head. In my evaluation process, I considered power amps by Carvin, QSC, Crown, and Yamaha (not exhaustive, by any means). I ultimately decided I could get most of the power I was looking for, plus complete backup utility, by purchasing a second bass head. So now I have Carvin R600 and R1000 heads - if I need tons of power, I can use both (will push at least 1300 watts combined, if needed). If one head goes down (or is out for repair) I have the other available. Most of my needs so far have been covered by just the R1000, but I bring the R600 to gigs anyway for backup (well, it's currently built into the RC210 combo I use for its 10" drivers).

Anyway - I found that the QSC and Carvin heads to come up really high in the performance per dollar dimension, so I would recommend a serious look at both brands. I find Carvin's power ratings kind of liberal, so you might compare ratings at equivalent distortion/frequency test points. Other than that, Carvin has good quality electronics. The QSC RMX series is decent, but the PLX series, despite its higher cost, is likely to be significantly better. Carefully compare specs and do searches on these forums - lots of people have comments about them. QSC's web site (http://www.qscaudio.com/) has particularly detailed spec sheets on their popular amp lines.

Originally posted by MikeyD Let me be a smart guy and suggest coupling your nice speakers to a big horn cabinet! Horn loading is one way to get around the SPL vs. Low F conundrum, but the cost is then size and weight!

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Oh yeah, exponential horns were a big deal for me 40 years ago. I got to actually see and diddle with the big one at the Rialto theatre when I was kid growing up in Boise, ID. The entire mouth of the horn was the movie screen. This monster was driven by a 5" (not a typo) driver, the time alignment problems with tap dancing vs sound were terrible.

Horns are a wonderful thing... for high frequencies. A bass horn suitable for a 5-string bass would have a 36 foot long throw, and require a mouth more than 9 foot square. The Klipschorns were truly amazing, and had a 40 Hz cutoff point, but required a house to do it [ grin ]

Your point about a second head is one of those "doh!" points I didn't think about. The obvious benefit is having a spare head if/when the other head craps out. Nothing like being 5 minutes away from opening the show, and all the Magic Smoke escapes from your amp. Once the Magic Smoke has been let out of the amp, it no longer works.

I guess one would have to shop around to find a device that will split a passive bass output into two amp heads without degrading the signal. The word "Raven Labs" sticks in my mind, but I don't know why..

It would be kinda cool to have a 2nd SWR 750 head in operation. Man... carrying all this junk... yuck.

I dig what you said about horns. And it was right on to mention Klipsch, because Paul K. wanted to minimize the amount of cone movement while still getting strong fundamentals out efficiently.

The Magic Smoke comment made me LOL!

On the subject of 2nd bass heads: I wrestled with how best to connect my two Carvins for quite awhile. Then I studied the wiring diagram I asked Carvin to send, and discovered that if I take the effects send of the "master" (to which I plug in my bass) and run it into the effects return of the "slave" head, all is utopia in amp-land (no ground loop hum, perfect signal level match, etc.)! It works great with the Carvins because I can set the primary pre-amp EQs and compression on the master head, but use the graphic EQs on the two heads to separately adjust what gets to their respective speaker cabinets. And I can individually adjust their output gains. Works great. I'm not very familiar with the Eden heads, but I'd guess you might be able to rig up something similar. If they have preamp send/return loops as well, that might serve as another option. You might also think about getting a different power output head. For example, if you have a 400-watt head and add an 800-watt, then you could have the flexibility of 400, 800, or 1200-watt capability, depending on the situation. My Carvin heads are both stereo, but can be bridged as well. This allows incredible flexibility to drive almost any kind of speaker combination.

P. Klipsch is a hero of mine. I admire him for his thinking outside the box. Pardon the bad pun. I got to hear one of his corner horns many years ago and was very impressed. I looked into building one but found back then I didn't have the skills necessary to accurately build one. I could do it today, but would have no place to run it. My home system could use a subwoofer, so I will use a Rockford instead.

Thinking outside the box - LOL! Yes, I believe the greatest engineers are the most creative and try to reject the popular thinking of their day. I think Bob Carver is another example of a gifted audio engineer who does "weird" things that turn the world upside down and show everyone a thing or two.

A few years ago I thought about getting a subwoofer for my small livingroom; I came across a good deal on a pair of JBL CF150's - which have 15" woofers, are rather large, and flat down to maybe 35 Hz (-6 dB at 32 Hz). For the first time ever I have a pair of hi-fi speakers for which I never use the loudness button on my receiver. The bass extension is nice. They are ported cabs, so it falls rather rapidly below 30 Hz., though. Anyway - an inexpensive solution to hi-fi, if one can deal with declining output below 30 Hz. (there's not much music down there anyway - and it's more felt than heard).

I'm kinda curious as to what is out there for high power amps, rackable, and if there are any transformer based (non-switching) power supplies still in production.

I have a question into SWR about my Bass 750 being switched or transformer. I suspect transformer, because the amp weighs 33 pounds. For me, this is a Good Thing as I have reliability issues with switching power supplies.

Hey bgavin,
I've been meaning to post a reply here for a while but I've been working 16 hour days this week and I haven't had much time for posting, my posts tend to be long, as is typical for the techno-geeks around here . First, I'm pretty sure the 750 has a standard transformer PSU, with the associated big filter caps. I have problems with switch mode PSUs, but my main problem isn't with reliability but with low frequency and transient performance. Switch mode amps simply do not perform as well in these areas. Myself and MikeyD have had some discussions on this topic in past threads, but I don't think we've foud a definitive reason why. It probably has to do with the energy storage capacity of the filter caps. Here's what I think goesa on: The larger caps in conventional power supplies can provide more reserve energy when an amp is operating near its limits, so conventional PSU amps deal with transients better. I work in the pro audio racket and I've had the opportunity to A-B test lots of amplifiers. In one particular test we AB'ed a Crown K2 (switch mode) and a Crown Macrotech 2400 (conventional) on Meyer Sound double 18 subwoofers. The K2 was rated more powerful than the Macrotech but the macrotech blew the K2 away on subs. Much more powerful and solid feeling. Damping factors were essentially the same so that wasn't an issue.
Anyway, if you're looking for lots of power you might want to look into PA amps. Be warned, they're expensive! There are tons of them with conventional PSUs. These are actually still more common than switch mode ones in this area. My faves ( based on low freq performance and reliability) are Crown's Macrotech series, QSCs Mx and Ex series, EV's P series, and Crest's 001 series. These amps have proven to be very powerful and reliable. They all weigh a ton (ie macrotech 2400 -70 lbs, EV P3000 75 lbs) due to the big power trannies and they are pretty pricey. You should be able to find a used QSC mx 1500 (500 w/channel @ 4 Ohms or 1000 W bridged @ 8 ohms, I think) for a pretty decent price (or maybe an mx 2000). They're very reliable, I know people that have been using the same ones for 15 years without a problem. Avoid the mxA series, they have a hybrid psu (some elements of both types, they call it two-tier or something) and are neither as reliable or as powerful as the mx series. If you're looking for huge amounts of power this might be a direction to look in. I have to go to work again so I have to cut this off here for now (I could yak about it forever). Cheers,

They all weigh a ton due to the big power trannies and they are pretty pricey.

They're very reliable, I know people that have been using the same ones for 15 years without a problem.

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Mr. Goat, I am in your debt for the knowledge transfer... my thanks. As for the SWR 750, I agree. When my query to SWR comes back (next year), I'll know for sure, but I think it is a safe bet. It weighs 33 pounds.

It makes sense that the PA amps are transformer types. I think they are called upon to have a higher standard of performance and reliability than a musician's amp. This may be a silly opinion, but it is a gut feel. And... those amps are priced accordingly. Crowns were killer years ago, and I have no doubt they are killer today. Years ago, IBM went with switching supplies, and I am certain is was for cost reasons, not reliability. I just have an issue with switching supplies...

As for the cost of PA amps, money is not an object. I don't like to piss away cash, so I try and do my research and buy it right the first time. I'm not at all dissatisfied with the SWR 750 except it just doesn't have enough power for my particular application. Some of my buds talk about not liking the SWR sound, but I have no experience in this area as I'm a newbie bassist. My years of playing are on 6-strings, Hammonds, and banjos. To my ears, the SWR 750 sounds just fine through my cabs.

The weight is annoying, but I am already carrying more than a single trip from the truck now. Adding 40 more pounds isn't a back breaker. My two cabs each weigh 150 pounds fully dressed. I have more design ideas for a smaller cab, but that is still on the drawing board.

Since you are in the audio racket, perhaps I can bounce my ideas off you. I'm tinkering with the idea of going component: a good bass-specific preamp, EQ, Rane Crossover, and power amp.

It is my understanding the "right" way to do the connections is balanced XLR between all the components.

The reason for using a crossover would only be for bi-amping the mid-bass drivers installed in my bass cabinets. The purpose is to avoid building passive 24 dB Linkwitz-Riley crossovers capable of passing 1,000 watts. This may be a crummy reason to bi-amp... dunno just yet.

I've been advised to look into the Aguilar, Demeter, Alembic, Ampeg, and Eden preamps. I think the deciding factor will be XLR output and tone. I'd rather have EQ and Xover as separates.

Originally posted by MikeyD Then I studied the wiring diagram I asked Carvin to send, and discovered that if I take the effects send of the "master" (to which I plug in my bass) and run it into the effects return of the "slave" head, all is utopia in amp-land (no ground loop hum, perfect signal level match, etc.)!

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mikey d, i don't understand how this increases power, since every effects loop i've seen comes before the power amp. are carvins different?

Originally posted by alembicbones My rig is an Alembic F-1X preamp, into an Alembic SF-2 Superfilter, then to a Stewart World 1.2 Power amp. I have an Eden d410T(8 ohm) and a D 410XLT(8 ohm).

I will always have a Stewart amp driving my speakers.

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Bones, they say the Alembic F-1X shares the same circuity design as the Fender Dual Showman... somehow this gives me a negative connotation. Nothing factual, but it strikes me emtionally some how.

Is this "good" or "bad" as a comparison? I don't know how I would characterize the tone. My only real experience, tonewise is with the SWR 750.

I read the BP review on the SVT-4Pro and they criticized it in the same manner as the SWR Mo' Bass, which is cheap construction of the pots directly attached to the circuit board. This gives me real cold feet..

Originally posted by dancehallclasher mikey d, i don't understand how this increases power, since every effects loop i've seen comes before the power amp. are carvins different?

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I was speaking of how to make one amp head a slave to another acting as the master. You are correct - the effects loop comes before the power amp sections. But what I was talking about was to take the "mostly preamplified" signal from the effects send of the *master* head and run it into the effects return of the *slave* head. The signal level is a perfect match, and most of the preamp processing from the master head feeds the power amps in both the master and slave heads. The result is you drive two heads by using the preamp of one, and get the potential power output of both. I hope this clarifies things.
- Mike

The Alembic site is very weak on details. Can you provide more detail about the F-1X especially in the crossover frequency, and where the tone controls take effect?

I'm disappointed in the built-in crossover, because it uses a gentle slope instead of a 24dB Linkwitz-Riley type. The mid-bass driver must extend twice as far into the bass region than it would with a 24dB slope. Also, the L/R crossovers have solved the reverse phasing issue that is inherent in 12dB slope designs.

I've been doing a lot of looking, and none of the preamps I've seen really have all that I am looking for. The Eden Navigator seems to come the closest as far as function goes.

Bones, can you make a comparison between the Ampeg and Alembic preamps as to tone?

Here's my $0.02 on power amps. I played quite a few of them before I got my Mackie 1400i. First, it's a very efficient 1400 watts. Second, it has an adjustable low-cut filter, to keep those power robbing low rumbles out of the mix, and finally, it's built like a tank and has a built in crossover for biamping. I suggest you give this amp a shot sometime.